<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>综合案例css基础选择器</title>
    <style>
        .box
        {
            width:100px;
            height: 100px;
            font-size: larger;
        }
        .first
        {
            background-color: red;
        }
        .second
        {
            background-color: green;
        }
        .bolder
        {
            font-weight: bolder;
        }
        
    </style>
    <link rel="stylesheet" href="">
</head>
<body>
    <div class="first box bolder" > heihei</div>
    <div class="box second " > hehe</div>
    <div class="box first" ><strong> nihao</strong></div>
    <div  class="bolder" > hehe</div>
</body>
</html>